Analysis on Fabrication of AlN/GaN/AlN Quantum-Well THz Devices with a Phononic–Excitonic–Radiative Model

AlN/GaN/AlN quantum wells offer a compelling materials platform for terahertz (THz) device fabrication, combining an ultra-large conduction-band offset, LO-phonon energies sufficient to suppress thermal backfilling, and excitonic resonances that can be engineered through confinement. This paper presents a fabrication-oriented model that integrates phononic, excitonic, and radiative design considerations into a coherent process flow. We first establish the physical rationale for the AlN/GaN/AlN double-barrier architecture, emphasizing the role of the 92 meV GaN LO phonon in enabling high-temperature THz operation and the influence of phonon screening on excitonic states in atomically thin wells. A fabrication sequence is then detailed, covering plasma-assisted molecular beam epitaxy with indium-surfactant-assisted interface engineering, ex situ characterization by high-resolution X-ray diffraction and transmission electron microscopy, and device processing into mesa-isolated resonant-tunneling and intersubband structures. We propose a phononic–excitonic–radiative co-design methodology in which LO-phonon scattering rates, exciton binding energies, and intersubband oscillator strengths are evaluated self-consistently before growth, and we discuss how measured structural parameters feed back into the model. Critical challenges—including interface roughness, polarization-induced field nonuniformity, and the trade-off between barrier thickness and tunneling current—are analyzed. The model provides a practical route toward reproducible AlN/GaN/AlN THz devices and identifies the metrology and modeling gaps that must be closed for room-temperature operation.